Tropical countries' per capita incomes could more than double if they managed to reduce their health burden from vector-borne and parasitic diseases (VBPDs) to that seen in temperate countries, a study has found.

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The study says that poor economic performance is caused partly by high disease burden, which is in turn affected by biodiversity.

The findings that health conditions affect economies, and that loss of biodiversity could exacerbate the situation, have direct policy implications, says the study published in PLoS Biology last month (27 December). The health benefits of biodiversity could be given a financial value based on the income it generates, it adds.Although VBPDs remain a leading cause of death and disability in poor countries, there is debate over their relative impact on global poverty patterns, the paper says.

Researchers from Harvard Medical School and Princeton University in the United States and from Université de Cergy-Pontoise in France set out to examine whether these diseases only played a historical role in delaying tropical countries' growth by limiting foreign investment and institutions' development, or whether environmental factors present in the tropics are the key element driving the VBPDs — which in turn still harming wealth production today.

If disease is still hindering development, then healthcare improvements should be made a key part of macroeconomic strategies and foreign economic aid, and not only be done for humanitarian reasons, the paper argues.

The researchers used models to estimate the relative effects of disease burden and per capita income on each other, controlling for other factors.

The findings bolster the case for targeting diseases to lessen their impact on tropical countries' economic development, according to Matthew Bonds, lead author from Harvard Medical School.

"Primary healthcare and low-cost drugs can treat the vast majority of infections," he says. "In many cases, the economic cost of treating disease may be lower than the cost of not treating it, given the potential long-term economic consequences."

The paper also found that biodiversity loss is likely to damage the economy by causing more disease. For example, if a country with relatively high biodiversity, such as Indonesia, were to lose 15 per cent of its biodiversity, the disease burden would be expected to rise by about 30 per cent, it says.

This is likely to be because higher biodiversity also means there are more species to prey on VBPD parasites and vectors, which spend much of their life cycles outside humans, unlike directly transmitted diseases, and so depend more on the environmental conditions, according to the paper.